1. Technical Field
The disclosure relates to a carbon nanotube needle and the method for making the same.
2. Discussion of Related Art
Carbon nanotubes (CNTs) produced by means of arc discharge between graphite rods were first discovered and reported in an article by Sumio Iijima, entitled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). CNTs also feature extremely high electrical conductivity, very small diameters (much less than 100 nanometers), large aspect ratios (i.e. length/diameter ratios greater than 1000), and a tip-surface area near the theoretical limit (the smaller the tip-surface area, the more concentrated the electric field, and the greater the field enhancement factor). These features tend to make CNTs ideal candidates for use in many materials and devices, such as composite materials, field emission devices, and micro electrical devices.
Generally, the tip-surface area of a CNT is very small. A single CNT is often used as a needle (i.e., probe, or sharp tip structure) connected to a base. The CNT needle with the base is used as a field emission electron source or a detecting probe. The methods adopted for forming the CNT needle with base mainly include mechanical and in situ synthesis methods. One mechanical method involves coating a base (or a cantilever of an atomic force microscope (AFM)) with an adhesive and touching it to a CNT array, and pulling one CNT away adhered to the base. However, because CNTs are so small, using this method is hard to control. Further, the CNT needle may easily separate from the base. Thus, the performance of the field emission electron source or detecting probe of AFM will be decreased and have short life.
One in-situ synthesis method is performed by coating metal catalysts on a base and synthesizing a CNT directly on the base by means of chemical vapor deposition (CVD). However, because CNTs have a small diameter, the interface of the CNT and the base will be small, and the mechanical connection between the CNT and the base will generally be relatively weak and, thus, unreliable. Further, it is difficult to grow only one CNT on the base.
What is needed, therefore, is an improved CNT needle and method for making same.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the present method, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.